HMT structure

Abstract

In the HMT structure of the present invention, the first and second elements of the planetary gear mechanism input power from the drive source and the HST, respectively, and the third element outputs a composite power. The HMT structure of the present invention comprises: a mechanical rotation applying mechanism capable of inputting power at a speed that causes the third element to be in an output zero state to the second element without passing through the HST; an HST-side clutch mechanism that engages / disengages the transmission from the HST to the second element; and a mechanical transmission-side clutch mechanism that engages / disengages the transmission to the second element via the mechanical rotation applying mechanism. If the shift operating lever is operated toward the parking position along a second operating direction that is different from the first operating direction of the shift operating HST, the HST-side clutch mechanism switches from the engaged state to the disengaged state and the mechanical transmission-side clutch mechanism switches from the disengaged state to the engaged state, thereby reliably presenting the output zero state of the third element.

Description

Technical Field

[0001] The present invention relates to a hydrostatic-mechanical continuously variable transmission structure (HMT structure) having a hydrostatic continuously variable transmission mechanism (HST) and a planetary gear mechanism. Background Art

[0002] The HMT structure, which is a combination of an HST and a planetary gear mechanism, is advantageously used in the transmission path of the travel system of working vehicles such as combine harvesters and tractors.

[0003] Japanese Patent Gazette No. 5822761 (hereinafter referred to as Patent Document 1) discloses a work vehicle in which an HMT structure is applied to a travel system transmission path. The HMT structure is configured such that the output rotational power of a planetary gear mechanism is set to zero speed by shifting the HST to a set intermediate speed between the maximum speed on the reverse side and the neutral speed. As the HST shifts from the set intermediate speed to the maximum speed on the reverse side, the output rotational power of the planetary gear mechanism is accelerated toward the reverse side, and as the HST shifts from the set intermediate speed to the maximum speed on the forward side via the neutral speed, the output of the planetary gear mechanism is accelerated toward the forward side.

[0004] The HMT structure described in Patent Document 1 can drive the work vehicle in both forward and reverse directions by the shifting operation of the HST without the work vehicle being provided with a separate forward and reverse switching mechanism, and is useful in that the speed range on the forward side is wider than that on the reverse side.

[0005] However, the conventional HMT structure has difficulty in presenting (appearing) a zero-speed state of the output (the zero-speed state of the output rotational power of the planetary gear mechanism), and when applied to a travel system transmission path, there is a problem in that it is difficult to present a travel stop state of the work vehicle.

[0006] That is, in order to make the output of the previous HMT structure become a zero-speed state, it is necessary to manufacture the HST and the connecting rod mechanism between the HST and the shift operating lever in such a way that the output rotational power of the HST accurately becomes the set intermediate speed when the shift operating lever used for shifting the HST is located at a set intermediate speed position corresponding to the set intermediate speed of the HST.

[0007] Furthermore, the output rotational power of the HST may unexpectedly fluctuate from a set intermediate speed due to pulsation of the HST hydraulic oil, and it is difficult to maintain the output zero speed state of the HMT structure.

[0008] Furthermore, in a work vehicle in which the HMT structure is provided in a transmission path of a running system, there is also a problem in that it is difficult to tow the work vehicle in the event of a breakdown or the like.

[0009] Specifically, when towing a work vehicle in which the HMT structure is installed in the travel transmission path, the rotation of the travel components forces the hydraulic motor of the HST, which is operatively coupled to the travel components, to rotate. The hydraulic motor is fluidly connected to the HST's hydraulic pump via a pair of hydraulic oil passages and is operatively coupled to a drive source such as an engine, preventing it from rotating freely.

[0010] Therefore, if the hydraulic motor is forced to rotate as the travel component rotates during towing of the work vehicle, the discharge oil from the hydraulic motor will flow into one of the pair of working oil circuits while the hydraulic pump cannot rotate due to the working connection with the drive source, and the rotation of the hydraulic motor will be hindered by the hydraulic pressure of the working oil circuit on one side. Summary of the Invention

[0011] The present invention has been made in view of the above-mentioned conventional technology, and an object of the present invention is to provide an HMT structure including an HST and a planetary gear mechanism, capable of outputting bidirectional rotational power on the forward and reverse sides and capable of reliably exhibiting an output zero state.

[0012] In order to achieve the above-mentioned purpose, the first scheme of the present invention provides an HMT structure, comprising: an HST, which continuously changes the speed of the rotational power input from the driving source to the pump shaft in a working (actuating) manner and outputs it from the motor shaft; a planetary gear mechanism, including a first element that inputs the rotational power of the reference speed transmitted from the driving source, a second element that can input the rotational power of the motor shaft, and a third element that outputs the synthetic rotational power of the first and second rotational powers; an HMT output shaft, which is operatively connected to the third element; a speed change operating lever, which can change the speed along the first operating direction to the forward side and the reverse side with a zero speed position clamped, and is operatively connected to the output adjustment member of the HST in a manner that the rotation speed of the motor shaft changes according to the operating position of the first operating direction; a mechanical rotation applying mechanism, which can input the rotational power from the driving source to the second element without passing through the hydraulic transmission path of the HST, and can make the synthetic rotation of the third element The rotational power of the rotational speed at which the rotational force becomes zero speed is input to the second element; the HST side clutch mechanism engages / disengages the power transmission from the motor shaft to the second element; and the mechanical transmission side clutch mechanism engages / disengages the power transmission from the drive source to the second element via the mechanical rotation applying mechanism. The HST and the planetary gear mechanism are constructed so that when the speed change operating lever is in the zero speed position, the synthetic rotational power of the third element becomes zero speed, and as the speed change operating lever is operated from the zero speed position to the forward side and the reverse side, the synthetic rotational power of the third element is accelerated toward the forward side and the reverse side, respectively. The speed change operating lever can be operated from the zero speed position to the parking position along a second operating direction different from the first operating direction. According to the operation of the speed change operating lever to the parking position, the HST side clutch mechanism switches from the engaged state to the disengaged state and the mechanical transmission side clutch mechanism switches from the disengaged state to the engaged state.

[0013] According to the HMT structure of the first embodiment of the present invention, bidirectional rotational power on the forward and reverse sides can be output from the HMT output shaft, and the output zero state of the HMT output shaft can be obtained when the rotational power is transmitted through a mechanical rotation application mechanism instead of a hydraulic transmission path through the HST, and the output zero state of the HMT output shaft can be reliably presented.

[0014] Therefore, if the HMT structure is applied to the travel transmission path of a work vehicle, the vehicle can be moved forward and reversed without providing the work vehicle with a separate forward and reverse switching mechanism, and the work vehicle can be reliably prevented from moving at a creeping speed against the operator's will.

[0015] In the first scheme, it is preferred that the speed change operating lever has a first operating shaft supported to rotate freely around an axis, a second operating shaft supported to the first operating shaft in an orthogonal state, a lever body that is manually operated, a connecting member that connects the base end of the lever body to the second operating shaft, and a lever guide provided with a guide groove for guiding the lever body, so that the lever body, the connecting member, the second operating shaft and the first operating shaft can be rotated integrally around the axis of the first operating shaft to present an operation along the first operating direction, and the lever body and the connecting member can be rotated around the axis of the second operating shaft to present an operation along the second operating direction.

[0016] The guide groove includes a first groove for guiding the lever body along the first operation direction and a second groove for allowing the lever body to move in a second operation direction only when the lever body is located at a zero speed position with respect to the first operation direction.

[0017] More preferably, the shift operating lever includes an urging member that urges the lever body and the connecting member toward a parking position around the axis of the second operating shaft.

[0018] In order to achieve the above-mentioned object, the second embodiment of the present invention provides an HMT structure, comprising: an HST, which continuously changes the speed of the rotational power input from the driving source to the pump shaft in an operative manner and outputs it from the motor shaft; a planetary gear mechanism, including a first element that inputs the rotational power of the reference speed transmitted from the driving source, a second element that can input the rotational power of the motor shaft, and a third element that outputs the combined rotational power of the first and second rotational powers; an HMT output shaft, which is operatively connected to the third element; a speed change operating lever, which can be operated to change the speed in a first operating direction to the forward side and the reverse side with a zero speed position sandwiched therebetween, and is operatively connected to the output adjustment member of the HST in such a manner that the rotation speed of the motor shaft changes according to the operating position in the first operating direction; a mechanical rotation applying mechanism, which can input the rotational power from the driving source to the second element without passing through the hydraulic transmission path of the HST, and can input the rotational power of the combined rotational power of the third element to the second element at a rotational speed that makes the zero speed of the combined rotational power of the third element; an HST side clutch mechanism, which can input the rotational power from the motor shaft to the second element; The first clutch mechanism is configured to engage / disengage power transmission to the second element; and a mechanical transmission side clutch mechanism engages / disengages power transmission from the drive source to the second element via the mechanical rotation applying mechanism, the HST and the planetary gear mechanism being configured so that when the shift operating lever is in the zero-speed position, the synthetic rotational power of the third element becomes zero speed, and as the shift operating lever is operated from the zero-speed position toward the forward side and the reverse side, the synthetic rotational power of the third element is accelerated toward the forward side and the reverse side, respectively, the shift operating lever being operable from the zero-speed position to the freewheel position (idling state) along a second operating direction different from the first operating direction, and being operable from the freewheel position to the parking position along a third operating direction different from the second operating direction, the HST side clutch mechanism is switched from the engaged state to the disengaged state in accordance with the operation of the shift operating lever toward the freewheel position, and the HST side clutch mechanism is maintained in the disengaged state and the mechanical transmission side clutch mechanism is switched from the disengaged state to the engaged state in accordance with the operation of the shift operating lever toward the parking position.

[0019] According to the HMT structure of the second scheme of the present invention, bidirectional rotational power on the forward and reverse sides can be output from the HMT output shaft, and the output zero state of the HMT output shaft can be obtained when the rotational power is transmitted through a mechanical rotation application mechanism instead of a hydraulic transmission path through the HST, and the output zero state of the HMT output shaft can be reliably presented.

[0020] Therefore, if the HMT structure is applied to the travel transmission path of a work vehicle, the vehicle can be moved forward and reversed without providing the work vehicle with a separate forward and reverse switching mechanism, and the work vehicle can be reliably prevented from moving at a creeping speed against the operator's will.

[0021] In addition, according to the HMT structure of the second embodiment of the present invention, it is possible to selectively present a normal speed change output state in which the rotational speed of the HMT output shaft changes according to the speed change operation of the speed change operating lever, an output zero state of the HMT output shaft, and a freewheel state in which the HMT output shaft is disconnected from the drive source and the HMT output shaft is allowed to rotate freely relative to the HST.

[0022] Therefore, when the HMT structure is applied to the travel transmission path of a work vehicle, the travel components of the work vehicle can be freely rotatable relative to the HST by assuming a free-wheel state, making it easy to forcibly tow the work vehicle.

[0023] In the second scheme, it is preferred that the speed change operating lever has a first operating shaft supported to rotate freely around an axis, a second operating shaft supported to the first operating shaft in an orthogonal state, a lever body that is manually operated, a connecting member that connects the base end of the lever body to the second operating shaft, and a lever guide provided with a guide groove for guiding the lever body, so that the lever body, the connecting member, the second operating shaft and the first operating shaft can be rotated integrally around the axis of the first operating shaft to present operations along the first and third operating directions, and the lever body and the connecting member can be rotated around the axis of the second operating shaft to present operations along the second operating direction.

[0024] The guide groove has a first groove that guides the rod body along the first operating direction, a second groove that allows the rod body to move to the freewheel position along the second operating direction only when the rod body is in the zero-speed position with respect to the first operating direction, and a third groove that allows the rod body to move to the parking position along the third operating direction only when the rod body is in the freewheel position with respect to the second operating direction.

[0025] More preferably, the shift operating lever includes an urging member that urges the lever body and the connecting member toward a side opposite to a freewheel position around the axis of the second operating shaft.

[0026] In order to achieve the above-mentioned purpose, the third scheme of the present invention provides an HMT structure, comprising: an HST, which continuously changes the speed of the rotational power input from the driving source to the pump shaft in a working manner and outputs it from the motor shaft; a planetary gear mechanism, including a first element for inputting the rotational power of the reference speed transmitted from the driving source, a second element for inputting the rotational power of the motor shaft, and a third element for outputting the combined rotational power of the first and second rotational powers; an HMT output shaft, which is operatively connected to the third element; a speed change operating lever, which can change the speed along the first operating direction to the forward side and the reverse side with a zero speed position clamped, and is operatively connected to the output adjustment component of the HST in a manner that the rotation speed of the motor shaft changes according to the operating position of the first operating direction; a mechanical rotation applying mechanism, which can apply the rotational power from the driving source to the second hydraulic transmission path without passing through the hydraulic transmission path of the HST. The gear mechanism is configured to input an element, and can input a rotational power of a rotational speed that makes the synthetic rotational power of the third element zero speed to the second element; an HST side clutch mechanism, which engages / disengages the power transmission from the motor shaft to the second element; and a mechanical transmission side clutch mechanism, which engages / disengages the power transmission from the drive source to the second element via the mechanical rotation applying mechanism. The HST and the planetary gear mechanism are configured so that when the speed shift operating lever is in the zero speed position, the synthetic rotational power of the third element becomes zero speed, and as the speed shift operating lever is operated from the zero speed position to the forward side and the reverse side, the synthetic rotational power of the third element increases in speed toward the forward side and the reverse side, respectively. When the speed shift operating lever is in the zero speed position, the HST side clutch mechanism switches from the engaged state to the disengaged state and the mechanical transmission side clutch mechanism switches from the disengaged state to the engaged state.

[0027] According to the HMT structure of the third scheme of the present invention, bidirectional rotational power on the forward and reverse sides can be output from the HMT output shaft, and the output zero state of the HMT output shaft can be obtained when the rotational power is transmitted through a mechanical rotation application mechanism instead of a hydraulic transmission path through the HST, and the output zero state of the HMT output shaft can be reliably presented.

[0028] Therefore, if the HMT structure is applied to the travel transmission path of a work vehicle, the vehicle can be moved forward and reversed without providing the work vehicle with a separate forward and reverse switching mechanism, and the work vehicle can be reliably prevented from moving at a creeping speed against the operator's will.

[0029] In various configurations of the HMT structure of the present invention, it is preferable that the HST-side clutch mechanism includes a bypass valve capable of switching between interruption and communication between a pair of hydraulic oil passages in the HST.

[0030] The HMT structure of the present invention may include an HMT housing that accommodates the HST and the planetary gear mechanism.

[0031] The HST comprises: the pump shaft, having a first end portion located on one side in the axial direction and inputting rotational power from a driving source in a working manner, and a second end portion on the other side in the axial direction; a hydraulic pump, supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the pump shaft; the motor shaft, arranged parallel to the pump shaft, having a first end portion on one side in the axial direction and a second end portion on the other side, outputting rotational power toward the second element via the first end portion; a hydraulic motor, supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the motor shaft, fluidically connected to the hydraulic pump via the pair of working oil passages; and the output adjusting member, capable of changing the volume of at least one of the hydraulic pump and the hydraulic motor, the HMT housing having an HST space for accommodating the hydraulic pump and the hydraulic motor and a planetary space for accommodating the planetary gear mechanism.

[0032] The planetary gear mechanism includes: a sun gear, which cannot rotate relative to the first end of the motor shaft and serves as the second element; a planetary gear, which meshes with the sun gear; an internal gear, which meshes with the planetary gear and serves as the first element; and a gear carrier, which supports the planetary gear so as to rotate freely around the axis and rotates around the axis of the sun gear in conjunction with the revolution of the planetary gear around the sun gear, and serves as the third element. The internal gear is configured to input rotational power from the drive source in the planetary space via the pump shaft or the HMT input shaft operatively connected to the pump shaft.

[0033] In the first structure, the mechanical rotation applying mechanism has a driving gear supported on the second end portion of the pump shaft and a driven gear supported on the second end portion of the motor shaft in a state of direct or indirect meshing with the driving gear, one of the driving gear and the driven gear is able to rotate freely relative to the corresponding shaft and the other cannot rotate relative to the corresponding shaft.

[0034] The mechanical transmission side clutch mechanism is capable of switching between engaging and disengaging one of the drive gear and the driven gear with respect to the corresponding shaft.

[0035] In the first configuration, the mechanical rotation applying mechanism and the mechanical transmission-side clutch mechanism are housed in a mechanical transmission housing connected to the HMT housing.

[0036] In the second structure, the mechanical rotation applying mechanism includes: a first drive gear, which is supported on the first end portion of the pump shaft in a manner that is non-rotatable relative to the first end portion; a first driven gear, which is supported on an idler shaft arranged in the planetary space and directly or indirectly meshed with the first drive gear; a second drive gear, which is supported on the idler shaft; and a second driven gear, which is directly or indirectly supported on the first end portion of the motor shaft in a state of directly or indirectly meshing with the second drive gear, wherein one of the first driven gear, the second drive gear and the second driven gear is able to rotate freely relative to the corresponding shaft and the remaining two gears are unable to rotate relative to the corresponding shaft.

[0037] The mechanical transmission side clutch mechanism is capable of switching the one gear on and off relative to the corresponding shaft.

[0038] In the third configuration, the mechanical rotation applying mechanism is a belt transmission mechanism operatively coupling the drive source and the motor shaft, and the mechanical transmission side clutch mechanism includes a tension pulley capable of switching between engagement and disengagement of power transmission of the belt transmission mechanism.

[0039] Among the various structures of the HMT structure of the present invention, it is preferred that the HST is constructed so that when the speed change operating lever is in the zero speed position, the rotational power of the motor shaft becomes a predetermined rotational speed on the reverse side between the neutral speed and the maximum speed on the reverse side, and as the speed change operating lever is operated from the zero speed position to the maximum speed position on the forward side, the rotational power of the motor shaft changes from the predetermined rotational speed on the reverse side via the neutral speed to the maximum speed on the forward side, and as the speed change operating lever is operated from the zero speed position to the maximum speed position on the reverse side, the rotational power of the motor shaft changes from the predetermined rotational speed on the reverse side to the maximum speed on the reverse side, and the planetary gear mechanism is constructed so that when the rotational power of the predetermined rotational speed on the reverse side is input to the second element, the synthetic rotational power of the third element becomes zero speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the power transmission of a work vehicle to which the HMT structure according to the first embodiment of the present invention is applied.

[0041] Figure 2 It is a cross-sectional view of the HMT structure of the first embodiment.

[0042] Figure 3 It is along Figure 2 Cross-sectional view along line III-III.

[0043] Figure 4 This is a hydraulic circuit diagram of the HMT structure according to the first embodiment.

[0044] Figure 5It is a plan view of the shift lever in the HMT structure of the first embodiment.

[0045] Figure 6 (a) and (b) are respectively along Figure 5 Side view and rear view of the shift lever along line VI(a)-VI(a) and line VI(b)-VI(b) in FIG.

[0046] Figure 7 This is a graph showing the relationship between the HST output and the HMT output in the HMT structure of the first embodiment.

[0047] Figure 8 It is a plan view of a shift lever in an HMT structure according to a modified example of the first embodiment.

[0048] Figure 9 This is a hydraulic circuit diagram of an HMT structure according to a second embodiment of the present invention.

[0049] Figure 10 It is a top view of the shift lever in the HMT structure of the second embodiment.

[0050] Figure 11 (a) and (b) are respectively along Figure 10 XI(a)-XI(a) line and XI(b)-XI(b) line of the shift lever are shown in FIG.

[0051] Figure 12 This is a cross-sectional view of an HMT structure according to a third embodiment of the present invention.

[0052] Figure 13 It is along Figure 12 Cross-sectional view along line XIII-XIII.

[0053] Figure 14 This is a schematic diagram of the power transmission of a work vehicle to which the HMT structure according to the fourth embodiment of the present invention is applied. DETAILED DESCRIPTION

[0054] Implementation Method 1

[0055] Hereinafter, one embodiment of the HMT structure of the present invention will be described with reference to the drawings.

[0056] Figure 1 A transmission schematic diagram of a work vehicle 1 to which an HMT structure (hydrostatic / mechanical continuously variable transmission structure) 200A according to the present embodiment is applied is shown.

[0057] like Figure 1As shown, the work vehicle 1 includes a drive source 5 , a travel member 6 , and the HMT structure 200A interposed in a travel transmission path from the drive source 5 to the travel member 6 .

[0058] The HMT structure 200A includes an HST (hydrostatic continuously variable transmission mechanism) 10 that continuously changes and outputs the rotational power input from the drive source 5, a planetary gear mechanism 100 that synthesizes the rotational power input from the drive source 5 and the HST 10 in a working manner and outputs the synthesized rotational power, and an HMT output shaft 350 that inputs the synthesized rotational power from the planetary gear mechanism 100 in a working manner and outputs it toward a driven component (in this embodiment, the traveling component 6).

[0059] Figure 2 A cross-sectional view of the HMT configuration 200A is shown.

[0060] in addition, Figure 3 Shown along Figure 2 Cross-sectional view along line III-III.

[0061] and, Figure 4 A hydraulic circuit diagram of the HMT configuration 200A is shown.

[0062] like Figures 1 to 4 As shown, the HST10 includes: a pump shaft 20, which is rotationally driven by the drive source 5 in a working manner; a hydraulic pump 25, which is supported on the pump shaft 20 in a relatively non-rotatable manner; a hydraulic motor 35, which is fluidically connected to the hydraulic pump 25 via a pair of working oil passages 601 and 602 and is rotationally driven hydraulically by the hydraulic pump 25; a motor shaft 30, which supports the hydraulic motor 35 so as to be relatively non-rotatable; and an output adjustment member 40, which changes the volume of at least one of the hydraulic pump 25 and the hydraulic motor 35 so as to steplessly change the ratio of the rotational speed of the HST output output from the motor shaft 30 to the rotational speed of the rotational power input to the pump shaft 20 (i.e., the speed ratio of the HST10).

[0063] like Figure 2 As shown, the pump shaft 20 has a first end 21 and a second end 22 located on one side and the other side of the axial direction respectively. The first end 21 is set as an input end connected to the driving source 5, and the hydraulic pump 25 is supported in the middle part between the first and second ends 21 and 22.

[0064] like Figure 2 As shown, in this embodiment, the motor shaft 30 is arranged in parallel with the pump shaft 20 and has first and second end portions 31 and 32 corresponding to the first and second end portions 21 and 22 of the pump shaft 20 .

[0065] The output adjustment member 40 is configured to be manually operable by a shift lever 700A (see FIG. 1 ) provided on the HMT structure 200A. Figure 4 ) is manually operated to make the HST output output from the motor shaft 30 continuously variable within a speed range spanning both forward and reverse directions.

[0066] In this embodiment, the HST 10 has a movable swash plate as the output adjustment member 40. The movable swash plate changes the capacity of the hydraulic pump 25 by swinging about a swing axis, and can swing to one side and the other side about the swing axis while sandwiching a neutral position where the discharge amount from the hydraulic pump 25 is zero.

[0067] When the movable swash plate is located at the neutral position, the discharge of the pressurized oil from the hydraulic pump 25 stops, and the HST 10 enters a neutral state in which the output of the hydraulic motor 35 is zero.

[0068] Furthermore, if the movable inclined plate swings from the neutral position to the positive rotation side around the swing axis, pressurized oil is supplied from the hydraulic pump 25 to the corresponding working oil circuit (for example, working oil circuit 601) in the pair of working oil circuits 601 and 602, and the corresponding working oil circuit 601 becomes the high-pressure side, and the other working oil circuit 602 becomes the low-pressure side.

[0069] As a result, the hydraulic motor 35 is rotationally driven in the forward direction, and the HST 10 enters a forward output state.

[0070] On the contrary, if the movable inclined plate swings from the neutral position to the reverse side on the other side of the swing axis, pressurized oil is supplied from the hydraulic pump 25 to the corresponding working oil circuit (for example, working oil circuit 602) in the pair of working oil circuits 601 and 602, and the corresponding working oil circuit 602 becomes the high-pressure side, and the other working oil circuit 601 becomes the low-pressure side.

[0071] As a result, the hydraulic motor 35 is rotationally driven in the reverse direction, and the HST 10 is brought into a reverse output state.

[0072] Furthermore, in the HST 10 , the volume of the hydraulic motor 35 is fixed by fixing the swash plate.

[0073] In the present embodiment, the HST 10 includes an oil supply mechanism 610 that supplies pressure oil supplied from a hydraulic source to the pair of hydraulic oil passages 601 and 602 .

[0074] Specifically, the work vehicle 1 includes an auxiliary pump 80 operatively driven by the drive source 5 as the hydraulic source.

[0075] like Figure 4As shown, the auxiliary pump 80 draws oil from an oil tank (not shown) via a suction path (not shown) and discharges the pressurized oil to the pressurized oil supply path 605 .

[0076] The pressure in the hydraulic oil supply path 605 is set to a predetermined hydraulic pressure by a pressure reducing valve 606 .

[0077] like Figure 4 As shown, the oil supply mechanism 610 has: a pair of oil supply passages 611, 612, the upstream side of which is fluidically connected to the pressure oil supply passage 605 and the downstream side of which is fluidically connected to the pair of working oil passages 601, 602 respectively; and a pair of stop valves 615, 616, which are respectively inserted into the pair of oil supply passages 611, 612 in a manner of allowing pressure oil to flow from the pressure oil supply passage 605 to the working oil passages 601, 602 and preventing reverse flow.

[0078] like Figure 4 As shown, the HMT structure 200A further includes an HST speed change operating mechanism 750 that operates the output adjustment member 40 in response to a human operation on the speed change operating lever 700A.

[0079] In this embodiment, if Figure 4 As shown, the HST speed change actuating mechanism 750 includes a hydraulic servo mechanism 760 that actuates the output adjusting member 40 using the pressurized oil from the assist pump 80 as hydraulic oil.

[0080] The hydraulic servo mechanism 760 includes: a cylinder 761; a piston 763, which divides the internal space of the cylinder 761 into a forward rotation chamber 761F and a reverse rotation chamber 761R in a liquid-tight manner and is accommodated in the internal space of the cylinder 761 in a slidable manner; and a switching valve 765, which switches the supply and discharge of pressurized oil relative to the forward rotation chamber 761F and the reverse rotation chamber 761R.

[0081] The switching valve 765 can selectively take a forward rotation position, a holding position and a reverse position. The forward rotation position is a position in which the pressure oil supply path 605 is fluidly connected to the forward rotation chamber 761F and the reverse chamber 761R is fluidly connected to the oil drain path 609. The holding position is a position in which the forward rotation chamber 761F and the reverse chamber 761R are respectively closed. The reverse position is a position in which the pressure oil supply path 605 is fluidly connected to the reverse chamber 761R and the forward rotation chamber 761F is fluidly connected to the oil drain path 609.

[0082] The piston 763 is operatively connected to the output adjustment member 40 .

[0083] Specifically, when pressurized oil is supplied to the forward rotation chamber 761F and discharged from the reverse rotation chamber 761R, the piston 763 moves in a direction that expands the forward rotation chamber 761F. Conversely, when pressurized oil is supplied to the reverse rotation chamber 761R and discharged from the forward rotation chamber 761F, the piston 763 moves in a direction that expands the reverse rotation chamber 761R. Furthermore, when the forward rotation chamber 761F and the reverse rotation chamber 761R are sealed, the piston 763 maintains the position at that point in time.

[0084] Here, the piston 763 is operatively connected to the output adjustment member 40 in the following manner: when it moves in the direction of expanding the forward rotation chamber 761F, the output adjustment member 40 moves toward the forward rotation side; when it moves in the direction of expanding the reverse rotation chamber 761R, the output adjustment member 40 moves toward the reverse rotation side; while maintaining the position at that point in time, the output adjustment member 40 is maintained at the position at that point in time.

[0085] Furthermore, when the output adjusting member 40 moves toward the forward rotation side, the output of the HST 10 is accelerated toward the forward rotation side, and when the output adjusting member 40 moves toward the reverse rotation side, the output of the HST 10 is accelerated toward the reverse rotation side.

[0086] The switching valve 765 is position-controlled according to a human operation on the shift lever 700A.

[0087] Figure 5 A top view of the shift operating lever 700A is shown.

[0088] in addition, Figure 6 (a) and (b) show the Figure 5 VI(a)-VI(a) line and VI(b)-VI(b) line of the shift lever 700A are shown in FIG.

[0089] like Figure 4 and Figure 6 As shown in (a), the speed change operating mechanism 750 is provided with an HST speed change arm 770 connected to the switching valve 765 so as to move the switching valve 765. The HST speed change arm 770 is operated according to a human operation on the speed change operating lever 700A.

[0090] like Figure 4 and Figure 6 As shown in FIG. 7 ( a ), in this embodiment, the shift operating lever 700A is operatively connected to the HST shift arm 770 via a mechanical link 780 .

[0091] Instead, the HST shift operating mechanism 750 may include an HST shift motor such as an electric motor for operating the HST shift arm 770 , and the operation of the HST shift motor may be controlled so that the HST shift arm 770 is operated in response to manual operation of the shift operating lever 700A.

[0092] like Figure 5 and Figure 6 As shown in (a), the shift lever 700A can be shifted in a first operation direction D1 toward the forward side F and the reverse side R with respect to the zero speed position O interposed therebetween.

[0093] In this embodiment, if Figure 6 As shown in (a) and (b), the shift operating lever 700A includes a first operating shaft 710 supported on a supporting body 705 such as an operating box in a manner that allows rotation around an axis, and a lever body 730 whose base end is directly or indirectly supported on the first operating shaft 710 in a manner that prevents relative rotation around the axis relative to the first operating shaft 710. The lever body 730 can be operated along a first operating direction D1 by swinging the lever body 730 around the axis of the first operating shaft 710.

[0094] In this embodiment, the shift operating lever 700A further includes a grip portion 735 provided at the distal end of the lever body 730 .

[0095] The HMT structure 200A of the present embodiment includes an operation position holding mechanism 790 that engages the shift operation lever 700A at a desired operation position with respect to the first operation direction D1.

[0096] like Figure 6 As shown in (b), the operating position maintaining mechanism 790 includes a disk 792 supported on the first operating shaft 710 in a manner that is non-rotatable relative to the axis, a pair of pads 794 arranged relatively to each other with the disk 792 clamped therebetween, and a force applying component 796 such as a coil spring for applying force to the pair of pads 794 in the clamping direction.

[0097] The operating position holding mechanism 790 connects the first operating shaft 710 to any position around the axis through the force of the force member 796. On the other hand, if an operating force exceeding the force of the force member 796 is applied to the shift operating lever 700, the first operating shaft 710 is allowed to rotate around the axis.

[0098] Figure 7 A graph showing the relationship between the rotational speed of the output of the HST 10 (rotational power of the motor shaft 30 ) and the rotational speed of the output of the HMT structure 200A (synthetic rotational power of the planetary gear mechanism 100 ) is shown.

[0099] In the HMT structure 200A of the present embodiment, when the output of the HST10 is set to the predetermined reverse rotation speed HST (Rs) between the neutral speed HST (N) and the maximum reverse rotation speed HST (Rmax), the output of the HMT structure 200A becomes zero speed 0, and as the output of the HST10 changes from the predetermined reverse rotation speed HST (Rs) via the neutral speed HST (N) to the maximum forward rotation speed HST (Fmax), the output of the HMT structure 200A changes from zero speed to the maximum forward rotation speed Fmax, and as the output of the HST10 changes from the predetermined reverse rotation speed HST (Rs) to the maximum reverse rotation speed HST (Rmax), the output of the HMT structure 200A changes from zero speed 0 to the maximum reverse rotation speed Rmax.

[0100] like Figure 5 As shown, the speed change lever 700A is operable along the first operating direction D1 between the Rmax position and the Fmax position corresponding to the speed variation range of the output of the HMT structure 200A, with zero speed 0 interposed therebetween.

[0101] That is, when the speed change lever 700A is located at zero speed 0 with respect to the first operation direction D1, the output of the HST 10 is set to the predetermined reverse rotation speed HST (Rs), and thus the output of the HMT structure 200A becomes zero speed 0.

[0102] As the shift operating lever 700A is operated from zero speed 0 along the first operating direction D1 to the forward side maximum speed position Fmax, the output of the HST10 changes from the reverse side predetermined speed HST (Rs) via the neutral speed HST (N) to the forward side maximum speed HST (Fmax), and accordingly, the output of the HMT structure 200A changes from zero speed 0 to the forward side maximum speed Fmax.

[0103] In addition, as the shift operating lever 700A is operated from zero speed 0 along the first operating direction D1 to the maximum speed position Rmax on the reverse side, the output of the HST10 changes from the predetermined speed HST (Rs) on the reverse side to the maximum speed HST (Rmax) on the reverse side, and accordingly, the output of the HMT structure 200A changes from zero speed to the maximum speed Rmax on the reverse side.

[0104] This configuration allows the output of the HMT structure 200A to be switched forward and reverse, and the absolute value of the forward maximum speed Fmax can be made larger than the reverse maximum speed Rmax, thereby expanding the variable speed range of the frequently used forward output compared to the reverse output.

[0105] In this embodiment, if Figure 5 and Figure 6As shown in (b), the shift operating lever 700A is configured to be operable from the zero-speed position 0 in a second operating direction D2 that is different from the first operating direction D1 in addition to the shift operation in the first operating direction D1.

[0106] This will be described later.

[0107] like Figure 2 and Figure 4 As shown, the planetary gear mechanism 100 has a sun gear 110, a planetary gear 120 meshing with the sun gear 110, an internal gear 130 meshing with the planetary gear 120, and a gear carrier (planetary carrier) 150 that supports the planetary gear 120 so that it can rotate freely around an axis and rotates around the axis of the sun gear 110 in conjunction with the revolution of the planetary gear 120 around the sun gear 110.

[0108] The planetary gear mechanism 100 is constructed such that the rotational power of the reference speed transmitted from the driving source 5 is input to the first element of the planetary three elements formed by the sun gear 110, the gear carrier 150 and the internal gear 130, and the rotational power of the HST10 (the rotational power of the motor shaft 30) is input to the second element, and these rotational powers are synthesized and output from the third element.

[0109] In the present embodiment, the internal gear 130 and the sun gear 110 function as the first and second elements, respectively, and the carrier 150 functions as the third element.

[0110] The sun gear 110 is coupled to the motor shaft 30 in a relatively non-rotatable manner.

[0111] like Figure 2 As shown, in this embodiment, the sun gear 110 is supported by the motor shaft 30 on the same axis as the motor shaft 30 so as to be non-rotatable relative to the motor shaft 30 around the axis.

[0112] The carrier 150 includes carrier pins 160 that support the planetary gears 120 so as to be rotatable about their axes, and a carrier body 170 that supports the carrier pins 160 so as to rotate about the axis of the sun gear 110 as the planetary gears 120 revolve around the sun gear 110 .

[0113] In this embodiment, the carrier body 170 includes first and second carrier bodies 171 and 172 that are separably connected to each other.

[0114] The first and second carrier bodies 171 and 172 define a space surrounding the sun gear 110 in a coupled state, and support one end portion and the other end portion of the carrier pin 160 in the axial direction, respectively.

[0115] In detail, the first gear frame body 171 close to the side of the HST10 has: a base end portion, which is supported by a partition wall 235 provided in the following HMT housing 210A in a relatively rotatable manner via a bearing component, and is provided with an axial hole for inserting the motor shaft 30; and a radial extension portion, which extends radially outward from the base end portion and is provided with a support hole on one end side of the axial direction of the gear frame pin 160.

[0116] The second carrier body 172 on the opposite side of the HST 10 is operatively connected to the HMT output shaft 350 in a relatively non-rotatable manner.

[0117] In the present embodiment, the second carrier body 172 includes a base end portion and a radially extending portion extending radially outward from the base end portion and provided with a support hole for supporting the other axial end side of the carrier pin 160 .

[0118] In the present embodiment, the rotational power extracted from the transmission path from the driving source 5 to the pump shaft 20 is transmitted to the internal gear 130 .

[0119] In detail, Figure 1 and Figure 2 As shown, the HMT structure 200A has an HMT input shaft 310, which is arranged on the same axis as the pump shaft 20, and is operatively connected to the drive source 5 on the upstream side in the transmission direction and is connected to the pump shaft 20 on the downstream side in a relatively non-rotatable manner.

[0120] In this embodiment, the HMT input shaft 310 is a hollow shaft, and is spline-coupled to the input-side transmission shaft 305 operatively coupled to the drive source 5 on the upstream side in the transmission direction, and is spline-coupled to the pump shaft 20 on the downstream side in the transmission direction.

[0121] The HMT input shaft 310 is further provided with a driving side transmission gear 312 in a middle portion between the upstream side and the downstream side in the transmission direction so as to be non-rotatable relative to each other.

[0122] In addition, in this embodiment, the driving side transmission gear 312 is formed integrally with the HMT input shaft 310, but of course the driving side transmission gear 312 can also be separated from the HMT input shaft 310 and supported in the middle of the axial direction of the HMT input shaft 310 in a manner that cannot rotate relative to each other.

[0123] The internal gear 130 includes a driven-side transmission gear 135 meshing with the driving-side transmission gear 312 . Rotational power from the driving source 5 is input to the internal gear 130 via the HMT input shaft 310 , the driving-side transmission gear 312 , and the driven-side transmission gear 135 .

[0124] In this embodiment, the internal gear 130 has: a base end portion, which is supported on the outer peripheral surface of the base end portion of the second gear frame body 171 in a relatively rotatable manner via a bearing component; an extension portion, which extends radially outward from the base end portion; and an outer end portion, which extends from the extension portion and is provided with a gear meshing with the planetary gear 120 and the driven side transmission gear 135.

[0125] In this embodiment, the HMT output shaft 350 is disposed on the same axis as the planetary gear mechanism 100 .

[0126] like Figure 2 and Figure 4 As shown, the HMT structure 200A of this embodiment further includes: a mechanical rotation applying mechanism 400A, which can input the rotational power from the driving source 5 to the second element without passing through the hydraulic transmission path of the HST 10; an HST side clutch mechanism 850, which enables the power transmission from the motor shaft 30 to the second element to be engaged / disengaged; and a mechanical transmission side clutch mechanism 450, which enables the power transmission from the driving source 5 to the second element to be engaged / disengaged via the mechanical rotation applying mechanism 400A.

[0127] In this embodiment, if Figure 3 and Figure 4 As shown, the HST side clutch mechanism 850 has a bypass valve 860 capable of switching the disconnection and connection between the pair of working oil circuits 601 and 602, and is configured such that the power transmission from the motor shaft 30 to the second element is engaged by disconnecting the pair of working oil circuits 601 and 602 through the bypass valve 860, and the power transmission from the motor shaft 30 to the second element is disconnected by connecting the pair of working oil circuits 601 and 602 through the bypass valve 860.

[0128] In this embodiment, if Figure 4 As shown, the HST-side clutch mechanism 850 includes a bypass passage 870 that connects the pair of hydraulic oil passages 601 and 602 .

[0129] The bypass valve 860 is configured to selectively take a bypass position and a cut-off position. The bypass position is a position in which the bypass passage 870 is in a connected state and the fluid between the pair of working oil passages 601 and 602 is connected, thereby cutting off the power transmission from the HST10 to the second element. The cut-off position is a position in which the bypass passage 870 is in a cut-off state and the pair of working oil passages 601 and 602 are disconnected, thereby connecting the power transmission from the HST10 to the second element.

[0130] In the present embodiment, the bypass valve 860 is provided as a solenoid valve whose position is controlled by the control device 900 provided in the HMT structure 200A in a state where the bypass valve 860 is urged toward the shutoff position by the urging member 862 .

[0131] That is, the bypass valve 860 is located at the cut-off position, which is the initial position, by the force member 862 in the initial state (normal state). If a control signal is input from the control device 900, it is located at the bypass position, which is the working position, against the force of the force member 862.

[0132] also, Figure 4 Reference numeral 890 is a bidirectional high-pressure reducing valve inserted in the connecting passage 865 connecting the pair of working oil passages 601 and 602, and is configured to release the pressure oil of one working oil passage to the other working oil passage when the hydraulic pressure of the working oil passage on one side exceeds a predetermined threshold.

[0133] The mechanical rotation applying mechanism 400A has a gear ratio set so that a rotational power having a rotational speed that makes the combined rotational power of the third element zero speed (hereinafter referred to as a predetermined zero speed rotational speed) is input to the second element.

[0134] In this embodiment, the mechanical rotation applying mechanism 400A has a driving gear 410 supported on the second end portion 22 of the pump shaft 20 and a driven gear 415 supported on the second end portion 32 of the motor shaft 30 in a state of direct or indirect engagement with the driving gear 410, and one of the driving gear 410 and the driven gear 415 can rotate freely relative to the corresponding shaft and the other cannot rotate relative to the corresponding shaft.

[0135] In this embodiment, if Figure 2 As shown, the driving gear 410 is supported by the corresponding pump shaft 20 in a relatively rotatable manner, and the driven gear 415 is supported by the corresponding motor shaft 30 in a relatively non-rotatable manner.

[0136] In addition, if Figure 3As shown, in this embodiment, the driving gear 410 and the driven gear 415 are meshed with each other via an idler gear 413 supported by an idler shaft 412 .

[0137] The mechanical transmission clutch mechanism 450 can switch between engagement and disengagement of the gears of the drive gear 410 and the driven gear 415 that are supported on corresponding shafts in a relatively rotatable manner with respect to the corresponding shafts.

[0138] As described above, in this embodiment, the driving gear 410 is supported by the corresponding pump shaft 20 in a relatively rotatable manner.

[0139] Therefore, the mechanical transmission side clutch mechanism 450 can switch the driving gear 410 between engagement and disengagement with respect to the pump shaft 20 .

[0140] Specifically, if Figure 2 and Figure 4 As shown, the mechanical transmission side clutch mechanism 450 includes: a clutch housing 460, which is supported on the second end portion 22 of the pump shaft 20 in a manner that is non-rotatable relative to each other; a friction plate group 465, including a driving side friction plate supported on the clutch housing 460 in a manner that is non-rotatable relative to each other and can move in the axial direction, and a driven side friction plate arranged opposite to the driving side friction plate when supported on the drive gear 410 in a manner that is non-rotatable relative to each other and can move in the axial direction; and a piston 470, which switches the friction engagement and release of the friction plate group 465.

[0141] In this embodiment, the mechanical transmission side clutch mechanism 450 is configured to operate the piston 470 using hydraulic pressure.

[0142] Specifically, the piston 470 partitions the clutch chamber 462 in a liquid-tight manner and is slidably accommodated in the clutch housing 460 .

[0143] like Figure 4 As shown, the mechanical transmission side clutch mechanism 450 further includes a clutch supply and exhaust passage 480 fluidly connected to the clutch chamber 462 on its downstream side and a clutch switching valve 485 fluidly connected to the upstream side of the clutch supply and exhaust passage 480 .

[0144] The clutch switching valve 485 is configured to selectively take a clutch engagement position in which pressure oil from a hydraulic source is supplied to the clutch supply and exhaust passage 480 , and a clutch release position in which the clutch supply and exhaust passage 480 and the oil exhaust passage 482 are fluidically connected.

[0145] In this embodiment, the pressurized oil in the pressurized oil supply path 605 is used as the hydraulic pressure source.

[0146] In the present embodiment, the clutch switching valve 485 is provided as a solenoid valve whose position is controlled by the control device 900 in a state where the clutch switching valve 485 is urged toward the clutch release position by the urging member 487 .

[0147] That is, the clutch switching valve 485 is located at the clutch release position, which is the initial position, through the force member 487 in the initial state (normal state). If a control signal is input from the control device 900, it is located at the clutch engagement position, which is the working position, against the force of the force member 487.

[0148] When the clutch switching valve 485 is located at the clutch engagement position and the pressurized oil is supplied to the clutch chamber 462 via the clutch supply and exhaust passage 480 , the piston 470 frictionally engages the friction plate group 465 .

[0149] As a result, power transmission from the pump shaft 20 to the drive gear 410 is engaged.

[0150] In addition, in this embodiment, if Figure 2 As shown, the mechanical transmission clutch mechanism 450 has a return spring 472 that presses the piston 470 in the direction away from the friction plate group 465. If the clutch switching valve 485 is in the clutch release position and the pressurized oil in the clutch chamber 462 is discharged through the clutch supply and exhaust passage 480 and the oil exhaust passage 482, the friction engagement of the friction plate group 465 is reliably released.

[0151] The bypass valve 860 of the HST side clutch mechanism 850 and the clutch switching valve 485 of the mechanical transmission side clutch mechanism 450 are located in their respective operating positions by the control device 900 when the shift operating lever 700A is operated from the zero speed position 0 along the second operating direction D2 to the parking position P.

[0152] First, operation of the shift operating lever 700A in the second operating direction D2 will be described.

[0153] In this embodiment, if Figure 5 、 Figure 6 (a) and Figure 6 As shown in FIG. 2( b ), the shift operating lever 700A includes, in addition to the first operating shaft 710 and the lever body 730 , a second operating shaft 720 supported substantially orthogonally to the first operating shaft 710 and a connecting member 740 supported by the second operating shaft 720 .

[0154] The connecting member 740 connects the base end of the rod body 730 to the second operating shaft 720 in such a manner that the rod body 730, the connecting member 740, the second operating shaft 720 and the first operating shaft 710 swing integrally around the axis of the first operating shaft 710 and the rod body 730 and the connecting member 740 swing around the axis of the second operating shaft 720.

[0155] Through this structure, the shifting operation of the shift operating lever 700 along the first operating direction D1 can be achieved by swinging the lever body 730, the connecting member 740, the second operating shaft 720 and the first operating shaft 710 integrally around the axis of the first operating shaft 710, and the operation of the shift operating lever 700 along the second operating direction D2 can be achieved by swinging the lever body 730 and the connecting member 740 integrally around the axis of the second operating shaft 720.

[0156] like Figure 6 As shown in (a), in this embodiment, the second operating shaft 720 is supported by the first operating shaft 710 in a state where one end portion and the other end portion extend outward while penetrating the first operating shaft 710 .

[0157] The connecting member 740 includes a pair of supporting pieces 742 supported at one end and the other end of the second operating shaft 720 , respectively, and a connecting piece 744 that has a gap with the first operating shaft 710 and connects the pair of supporting pieces 742 . The base end of the rod body 730 is connected to the connecting piece 744 .

[0158] The first operating shaft 710 is rotatably supported by the support body 705 , and the lever body 730 , the connecting member 740 , the second operating shaft 720 , and the first operating shaft 710 are integrally rotatable about the axis of the first operating shaft 710 .

[0159] Moreover, the second operating shaft 720 can rotate freely around the axis relative to the first operating shaft 710 and / or the pair of support pieces 742 can rotate freely around the axis relative to the second operating shaft 720, and the rod body 730 and the connecting member 740 can swing around the axis of the second operating shaft 720 within the range of the gap.

[0160] In the present embodiment, the shift operating lever 700A can be operated toward the parking position P along the second operating direction D2 only when it is located at the zero-speed position 0 with respect to the first operating direction D1.

[0161] Specifically, if Figure 5As shown, the shift operating lever 700A further includes a lever guide 800A having a guide groove 810A through which the lever body 730 is inserted.

[0162] The guide groove 810A includes a first groove 811 that guides the lever body 730 in the first operating direction D1 and a second groove 812 that allows the shift operating lever 700A to be operated in the second operating direction D2 only when the shift operating lever 700A is located at the zero speed position 0 with respect to the first operating direction D1.

[0163] The end position of the second groove 812 on the opposite side to the first groove 811 is set as the parking position P, and the position detection sensor 820 can detect that the shift lever 700A is located at the parking position P.

[0164] In the normal state when the shift operating lever 700A is not in the parking position P, the control device 900 causes the following HST transmission state to be presented: the bypass valve 860 is located in the cut-off position to engage the power transmission from the HST10 to the second element, and the clutch switching valve 485 is located in the clutch release position to cut off the mechanical transmission path for transmitting power from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A.

[0165] In the HST transmission state, rotational power of a speed corresponding to the operation position of the speed change operation lever 700A in the first operation direction D1 is output from the HMT output shaft 350 .

[0166] On the other hand, if the shift operating lever 700A is in the parking position P, the control device 900 causes the following mechanical transmission state to be presented: the bypass valve 860 is in the connecting position to cut off the power transmission from the HST10 to the second element, and the clutch switching valve 485 is in the clutch engagement position to connect the mechanical transmission path for transmitting power from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A.

[0167] As described above, the mechanical rotation applying mechanism 400A is configured to input the rotational power of the predetermined rotation speed for zero speed to the second element. Therefore, in the mechanical transmission state, the HMT output shaft 350 is forced to stop.

[0168] According to the HMT structure 200A having this configuration, the following effects can be obtained.

[0169] That is, by operating the speed change operation lever 700A along the first operation direction D1 from the zero speed position 0 toward the forward maximum speed Fmax and the reverse maximum speed Rmax, the forward rotational power and the reverse rotational power can be output from the HMT output shaft 350 .

[0170] Therefore, forward travel and reverse travel can be performed without providing a separate forward / reverse switching mechanism.

[0171] In addition, the planetary gear mechanism 100 is configured so that when the rotational power of the predetermined reverse rotational speed HST (Rs) is input to the second element, the synthetic rotational power becomes zero speed, and is set so that when the speed change operating lever 700A is in the zero speed position 0, the output of the HST10 becomes the predetermined reverse rotational speed HST (Rs).

[0172] According to this configuration, bidirectional rotational power, namely, forward rotational power and reverse rotational power, can be output from the HMT output shaft 350 , and the speed range of the forward rotational power, which is used more frequently, can be expanded.

[0173] Moreover, by operating the shift operating lever 700A from the zero-speed position 0 along the second operating direction D2 to the parking position P, rotational power of a predetermined speed for zero speed is input from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A without passing through the hydraulic transmission path of the HST10, so that the third element of the planetary gear mechanism 100 is reliably brought into the output zero state.

[0174] Therefore, when the HMT structure 200A is applied to the travel transmission path of the work vehicle 1 as in this embodiment, by positioning the shift lever 700A in the parking position P, the work vehicle 1 can be reliably prevented from moving at a creep speed against the operator's will.

[0175] That is, when the speed change lever 700A is located at the zero speed position 0, the HST 10 is set to output a rotational power of the predetermined reverse rotation speed HST (Rs) that makes the combined rotational power of the third element of the planetary gear mechanism 100 zero speed.

[0176] Therefore, theoretically, the combined rotational power of the third element can be made zero speed without inputting the rotational power of the predetermined zero speed rotation speed from the driving source 5 to the second element via the mechanical rotation applying mechanism 400A.

[0177] However, it is difficult to strictly maintain the output of the HST 10 at the predetermined reverse rotation speed HST (Rs). The output of the HST 10 may easily fluctuate from the predetermined reverse rotation speed HST (Rs) due to manufacturing errors of the HST 10 or pulsation of the hydraulic oil.

[0178] If the HST output varies from the predetermined reverse rotation speed HST(Rs), power at an unintended rotation speed will be output from the third element of the planetary gear mechanism 100 , and the work vehicle 1 may move at a creep speed.

[0179] In contrast, in the HMT structure 200A of this embodiment, as described above, if the shift lever 700A is located in the parking position P, the rotational power of a predetermined speed at zero speed is stably input to the second element via the mechanical rotation application mechanism 400A while the power transmission from the HST10 to the second element is released.

[0180] Therefore, the third element of the planetary gear mechanism 100 can be reliably brought into the output zero state.

[0181] like Figure 6 As shown in FIG. 2 ( b ), in this embodiment, the shift operating lever 700A further includes an urging member 840 for urging the lever body 730 and the connecting member 740 toward the parking position P around the axis of the second operating shaft 720 .

[0182] By providing the biasing member 840 , the shift lever 700A can be automatically positioned at the parking position P when the operating force is released in a state where the shift lever 700A is positioned at the zero speed position O with respect to the first operating direction D1 .

[0183] like Figure 2 As shown in FIG. 1 and FIG. 2 , the HMT structure 200A of the present embodiment further includes an HMT housing 210A that houses the HST 10 and the planetary gear mechanism 100 and supports the HMT output shaft 350 .

[0184] The HMT housing 210A is detachably connected to a mounting portion (the transmission 500 in this embodiment).

[0185] like Figure 2 As shown, the HMT housing 210A includes an HST space 211 for accommodating the hydraulic pump 25 and the hydraulic motor 35 , and a planetary space 212 for accommodating the planetary gear mechanism 100 .

[0186] In this embodiment, the HMT housing 210A includes a housing body 220A, and a first cover member 240 and a second cover member 260 detachably connected to the housing body 220A.

[0187] The shell body 220A has a hollow peripheral wall 230A with first and second openings 231 and 232 on one and the other sides in the axial direction, respectively, and a partition wall 235 at the axial middle position of the peripheral wall 230A that divides the internal space of the peripheral wall 230A into the HST space 211 and the planetary space 222.

[0188] The second cover member 260 is detachably connected to the housing body 220A so as to close the second opening 232 .

[0189] like Figure 2 and Figure 3 As shown, the second cover member 260 also functions as a port blocking block in which the pair of hydraulic oil passages 601 and 602 are formed.

[0190] The first cover member 240 is detachably connected to the housing body 220A so as to close the first opening 231 .

[0191] The first cover member 240 also functions as a mounting surface with respect to a mounting portion of the HMT housing 210A (in this embodiment, the transmission housing 510 of the transmission 500 ).

[0192] In the present embodiment, the HMT housing 210A is configured to support the HMT input shaft 310 .

[0193] Specifically, the HMT input shaft 310 is supported by the first cover member 240 and the partition wall 235 in the planetary space 212 so as to be rotatable around its axis.

[0194] The upstream side of the HMT input shaft 310 in the transmission direction is connected to the input-side transmission shaft 305 via an access hole (inlet) formed in the first cover member 240 .

[0195] The first end portion 21 of the pump shaft 20 passes through the partition wall 235 and is connected to the downstream side of the HMT input shaft 310 in the transmission direction.

[0196] In this embodiment, if Figure 2 As shown, the second end portion 22 of the pump shaft 20 passes through the second cover member 260 and extends outward. The driving gear 410 of the mechanical rotation applying mechanism 400A and the mechanical transmission clutch mechanism 450 are supported on the outwardly extending portion.

[0197] A mechanical transmission housing 280 is detachably mounted on the outer surface of the second cover member 260 .

[0198] The mechanical transmission housing 280 has an opening 282 that opens toward the second cover member 260 , and is attached to the second cover member 260 such that the opening 282 is closed by the second cover member 260 .

[0199] The mechanical rotation applying mechanism 400A and the mechanical transmission-side clutch mechanism 450 are housed in a mechanical transmission space defined by the mechanical transmission housing 280 and the second cover member 260 .

[0200] The motor shaft 30 is rotatably supported around its axis by the second cover member 260 and the partition wall 235 , with the first end 31 penetrating the partition wall 235 and protruding into the planetary space 212 , and the second end 32 penetrating the second cover member 260 and protruding into the mechanical transmission space.

[0201] The driven gear 413 of the mechanical rotation applying mechanism 400A is supported by the second end portion 32 of the motor shaft 30 in the mechanical transmission space.

[0202] The planetary gear mechanism 100 is housed in the planetary space 212 on the same axis as the motor shaft 30 .

[0203] The HMT output shaft 350 is connected to the gear frame 150 upstream in the transmission direction and is supported by the first cover member 240 so as to be rotatable about its axis in a state where its downstream side in the transmission direction is accessible from the outside through an access hole formed in the first cover member 240 .

[0204] In this embodiment, the HMT output shaft 350 is disposed on the same axis as the planetary gear mechanism 100 .

[0205] like Figure 1 As shown, the work vehicle 1 to which the HMT structure 200A of the present embodiment is applied includes the transmission 500 that changes the speed of the rotational power from the HMT structure 200A and outputs the rotational power to the travel member 6 .

[0206] The transmission 500 includes the transmission housing 510 , a transmission input shaft 515 supported by the transmission housing 510 , an auxiliary transmission drive shaft 520 and an auxiliary transmission driven shaft 530 , and an auxiliary transmission mechanism 525 for performing multi-stage speed change between the auxiliary transmission drive shaft 520 and the auxiliary transmission driven shaft 530 .

[0207] The HMT housing 210A is assembled to the transmission housing 510 in such a manner that the input-side transmission shaft 305 and the HMT output shaft 350 are connected to the transmission input shaft 515 and the auxiliary transmission drive shaft 520 , respectively.

[0208] In the work vehicle 1 , the travel members 6 are provided as a pair of left and right travel members.

[0209] Therefore, the transmission 500 further includes a pair of drive axles 545 , 545 that output drive force to the pair of travel elements 6 , 6 , respectively, and a differential mechanism 540 that differentially transmits the rotational power of the auxiliary transmission driven shaft 530 to the pair of drive axles 545 , 545 .

[0210] also, Figure 1 Reference numeral 535 denotes a parking brake mechanism for selectively applying braking force to the auxiliary transmission driven shaft 530 , and reference numeral 550 denotes a pair of travel brake mechanisms for selectively applying braking force to the pair of drive axles 545 , 545 .

[0211] As described above, in this embodiment, the shift operating lever 700A is not only operable in the first operating direction D1 but also operable in the second operating direction D2 toward the parking position P when the speed is zero relative to the first operating direction D1.

[0212] Instead of this, a shift operating lever 700A' operable only in the first operating direction D1 may be used.

[0213] Figure 8 A top view of the shift operating lever 700A' is shown.

[0214] The shift operating lever 700A′ includes the first operating shaft 710 and the lever body 730 , and is operable in a first operating direction D1 by swinging around the axis of the first operating shaft 710 .

[0215] Compared to the above-mentioned shift operating lever 700A, the above-mentioned shift operating lever 700A′ includes a lever guide 800A′ provided with a guide groove 810A′ instead of the above-mentioned lever guide 800A.

[0216] The guide groove 810A′ includes a first groove 811 .

[0217] In a modified example having the shift lever 700A', when the shift operating lever 700A' is located outside the zero speed position, the HST side clutch mechanism 850 is in an engaged state and the mechanical transmission side clutch mechanism 450 is in a disengaged state, and the output of the rotational speed corresponding to the operating position of the shift operating lever 700A' with respect to the first operating direction D1 is input from the motor shaft 30 to the second element, and when the shift operating lever 700A' is located at the zero speed position (parking position P), the HST side clutch mechanism 850 is switched from the engaged state to the disengaged state and the mechanical transmission side clutch mechanism 450 is switched from the disengaged state to the engaged state, thereby inputting the rotational power transmitted via the mechanical transmission path to the second element and the third element is forcibly set to a rotational stop state.

[0218] Implementation Method 2

[0219] Hereinafter, another embodiment of the HMT structure of the present invention will be described with reference to the drawings.

[0220] Figure 9 A hydraulic circuit diagram of an HMT structure 200B according to this embodiment is shown.

[0221] In the drawings of this embodiment, the same reference numerals are given to the same components as those in the first embodiment, and description thereof will be omitted as appropriate.

[0222] The HMT structure 200A of the first embodiment is configured to simultaneously switch the power transmission from the HST 10 to the second element of the planetary gear mechanism 100 from the engaged state to the disconnected state and the power transmission from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A from the disconnected state to the engaged state.

[0223] In contrast, the HMT structure 200B of the present embodiment is configured to selectively present an HST transmission state, a freewheel state, and a mechanical transmission state, wherein the HST transmission state is a state in which the power transmission from the HST10 to the second element is engaged and the power transmission from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A is cut off, the freewheel state is a state in which both the power transmission from the HST10 to the second element and the power transmission from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A are cut off, and the mechanical transmission state is a state in which the power transmission from the HST10 to the second element is cut off and the power transmission from the drive source 5 to the second element via the mechanical rotation applying mechanism 400A is engaged.

[0224] Specifically, the HMT structure 200B is different from the HMT structure 200A of the first embodiment in that the shift operating lever 700A is replaced with a shift operating lever 700B.

[0225] Figure 10 A top view of the shift operating lever 700B is shown.

[0226] in addition, Figure 11 (a) and (b) show the Figure 10 XI(a)-XI(a) and XI(b)-XI(b) are side and rear views of the shift lever 700B.

[0227] The shift lever 700B is operable from the zero-speed position O to the freewheel position F along a second operating direction D2 different from the first operating direction D1 , and is operable from the freewheel position F to the parking position P along a third operating direction D3 different from the second operating direction D2 .

[0228] Compared to the shift operating lever 700A, the shift operating lever 700B includes a lever guide 800B instead of the lever guide 800A.

[0229] like Figure 10 As shown, the rod guide 800B is provided with a guide groove 810B.

[0230] The guide groove 810B includes the first and second grooves 811 and 812 , and further includes a third groove 813 .

[0231] The end position of the second groove 812 on the opposite side to the first groove 811 is defined as a freewheel position F. The position detection sensor 830 can detect that the shift operating lever 700B is located at the freewheel position F.

[0232] The third groove 813 is configured to allow the shift operating lever 700B to be operated in the third operating direction D3 only when the shift operating lever 700B is located at the freewheel position F with respect to the second operating direction D2.

[0233] The end position of the third groove 813 on the opposite side to the second groove 812 is set as the parking position P, and the position detection sensor 835 can detect that the shift lever 700B is located at the parking position P.

[0234] The control device 900, when the shift operating lever 700B is in the normal state in which it is engaged in the first groove 811 (i.e., both the position detection sensors 830 and 835 are in the non-detection state), causes the following HST transmission state to be presented: the bypass valve 860 is located in the cut-off position to engage the power transmission from the HST10 to the second element, and the clutch switching valve 485 is located in the clutch release position to cut off the power transmission from the drive source 5 via the mechanical rotation applying mechanism 400A to the second element.

[0235] When the shift operating lever 700B is in the freewheel position F, the control device 900 causes the following freewheel state to be presented: the bypass valve 850 is moved from the disconnected position to the connected position to switch the power transmission from the HST10 to the second element from the engaged state to the disconnected state, and the clutch switching valve 485 is kept in the clutch release position to maintain the power transmission from the drive source 5 via the mechanical rotation applying mechanism 400A to the second element in the disconnected state.

[0236] In this free-wheel state, the travel member 6 and the planetary gear mechanism 100, which is operatively connected to the drive source 5, are disconnected by the HST-side clutch mechanism 850 and the mechanical transmission-side clutch mechanism 450, and the travel member 6 is in a freely rotatable state. Therefore, forced towing of the work vehicle 1 can be easily performed.

[0237] Furthermore, when the shift operating lever 700B is in the parking position P, the control device 900 causes the following mechanical transmission state to be presented: the bypass valve 860 is kept in the connected position to maintain the power transmission from the HST10 to the second element in a cut-off state, and the clutch switching valve 485 is moved from the clutch release position to the clutch engagement position to engage the power transmission from the drive source 5 via the mechanical rotation applying mechanism 400A to the second element.

[0238] According to the HMT structure 200B of this embodiment, the same effects as those of the first embodiment can be obtained, and the free-wheel state can be selectively exhibited.

[0239] Implementation 3

[0240] Hereinafter, another embodiment of the HMT structure of the present invention will be described with reference to the drawings.

[0241] Figure 12 A cross-sectional view of an HMT structure 200C according to this embodiment is shown.

[0242] in addition, Figure 13 Shown along Figure 12Cross-sectional view along line XIII-XIII.

[0243] In the drawings, the same reference numerals are given to the same components as those in the above-described embodiment, and description thereof will be omitted as appropriate.

[0244] In the HMT structure 200A of the first embodiment, the mechanical rotation applying mechanism 400A and the mechanical transmission-side clutch mechanism 450 are housed in the mechanical transmission housing 280 attached to the HMT housing 210A.

[0245] On the other hand, in the HMT structure 200C of the present embodiment, the mechanical rotation applying mechanism 400C and the mechanical transmission-side clutch mechanism 450 are housed in the planetary space 212 of the HMT housing 200C.

[0246] Specifically, compared with the HMT structure 200A of the first embodiment, the HMT structure 200C includes the HMT housing 210C instead of the HMT housing 210A, and includes the mechanical rotation applying mechanism 400C instead of the mechanical rotation applying mechanism 400A.

[0247] like Figure 12 and Figure 13 As shown, the mechanical rotation applying mechanism 400C is housed in the planetary space 212 and is configured to extract rotational power from a transmission path from the driving source 5 to the pump shaft 20 .

[0248] In detail, Figure 12 and Figure 13 As shown, the mechanical rotation applying mechanism 400C has: a first driving gear 420, which is supported on the first end portion 21 of the pump shaft 20 in a manner that is non-rotatable relative to the first drive gear 420; a first driven gear 425, which is supported on an idler shaft 422 provided in the planetary space 212 and directly or indirectly meshed with the first driving gear 420; a second driving gear 430, which is supported on the idler shaft 422; and a second driven gear 435, which is directly or indirectly supported on the first end portion 31 of the motor shaft 30 in a state of directly or indirectly meshing with the second driving gear 430, wherein the first driven gear 425, the second driving gear 430 and one of the second driven gear 435 can rotate freely relative to the corresponding shaft and the remaining two gears cannot rotate relative to the corresponding shaft.

[0249] In this embodiment, if Figure 12As shown, the second drive gear 430 is supported on the corresponding idler shaft 422 in a manner that allows for relative rotation, and the remaining first driven gear 425 and the second driven gear 434 are respectively directly or indirectly supported on the corresponding idler shaft 422 and the motor shaft 30 in a manner that prevents relative rotation.

[0250] In addition, in this embodiment, if Figure 12 As shown, the HST transmission shaft 320 is externally inserted into the first end portion 31 of the motor shaft 30 in a relatively non-rotatable manner, and the second driven gear 435 is supported by the HST transmission shaft 320 .

[0251] Furthermore, the sun gear 110 functioning as the second element is supported by the HST transmission shaft 320 in a relatively non-rotatable manner.

[0252] like Figure 12 As shown, the HMT housing 210C includes a housing body 220C, and the first cover member 240 and the second cover member 260 detachably connected to the housing body 220C.

[0253] The housing body 220C includes a hollow peripheral wall 230C having the first and second openings 231 and 232 and the partition wall 235 .

[0254] The peripheral wall 230C has a bulging wall 237 bulging radially outward in a circumferential portion of the middle region in the axial direction. Through the bulging wall 237, a clutch accommodating area 213 is provided in the planetary space 212, which expands radially outward from the area accommodating the planetary gear mechanism 100.

[0255] The shell body 220C also has a bearing plate 239 arranged in the planetary space 212 in a manner opposite to the bulging wall 237, and one end side of the idler shaft 422 is supported by the bearing plate 239 via a bearing component and the other end side is supported by the bulging wall 237 via a bearing component.

[0256] In addition, in this embodiment, the input-side transmission shaft 305 is deleted, and the upstream side of the HMT input shaft 310 in the transmission direction is connected to an external member (for example, the transmission input shaft 515).

[0257] The mechanical transmission side clutch mechanism 450 is capable of switching the engagement / disengagement of the gears supported on the corresponding shafts in a relatively rotatable manner among the first drive gear 420, the first driven gear 425, the second drive gear 430 and the second driven gear 435 provided in the mechanical rotation applying mechanism 400C relative to the corresponding shafts.

[0258] As described above, in this embodiment, the second drive gear 430 is supported by the corresponding idler shaft 422 in a relatively rotatable manner.

[0259] Therefore, the mechanical transmission clutch mechanism 450 can switch between engagement and disengagement of the second drive gear 430 with respect to the idler shaft 422 .

[0260] Specifically, if Figure 12 As shown, the clutch housing 460 is supported on the idler shaft 422 in a relatively non-rotatable manner within the clutch receiving area 213 of the planetary space 212 .

[0261] The driving side friction plate of the friction plate group 465 is supported on the clutch housing 460 in a manner that is non-rotatable and axially movable, and the driven side friction plate is supported on the second driving gear 430 in a manner that is non-rotatable and axially movable, and is arranged opposite to the driving side friction plate.

[0262] According to the HMT structure 200C having this configuration, the same effects as those of the first embodiment can be obtained, and elongation in the axial direction can be effectively prevented.

[0263] In addition, the mechanical rotation applying mechanism 400C has a first reduction gear train including the first driving gear 420 and the first driven gear 425 and a second gear train including the second driving gear 430 and the second driven gear 435, which can reduce the rotational power transmitted from the driving source 5 to the pump shaft 20 in two stages and transmit it to the second element, thereby increasing the freedom of setting the reduction ratio of the mechanical rotation applying mechanism 400C.

[0264] Implementation 4

[0265] Hereinafter, another embodiment of the HMT structure of the present invention will be described with reference to the drawings.

[0266] Figure 14 A power transmission diagram of a work vehicle 1 to which the HMT structure 200D of the present embodiment is applied is shown.

[0267] In the drawings, the same reference numerals are given to the same components as those in the above-described embodiment, and description thereof will be omitted as appropriate.

[0268] Compared with the HMT structure 200A of the first embodiment, the HMT structure 200D of the present embodiment includes a mechanical rotation applying mechanism 400D and a mechanical transmission side clutch mechanism 450D instead of the mechanical rotation applying mechanism 400A and the mechanical transmission side clutch mechanism 450 .

[0269] like Figure 14 As shown, the mechanical rotation applying mechanism 400D is provided as a belt transmission mechanism that operatively couples the driving source 5 and the motor shaft 30 .

[0270] In this embodiment, the mechanical rotation applying mechanism 400D has a first drive pulley 441a operatively connected to the drive source 5, a first driven pulley 442a operatively connected to the idler shaft 445, a first belt 443a wound around the first drive pulley 441a and the first driven pulley 442a, a second drive pulley 441b operatively connected to the idler shaft 445, a second driven pulley 442b operatively connected to the motor shaft 30, and a second belt 443b wound around the second drive pulley 441b and the second driven pulley 442b.

[0271] The mechanical transmission-side clutch mechanism 450D includes a tension pulley 490 that can selectively engage / disengage the mechanical rotation applying mechanism 400D in applying tension to the belt.

[0272] In this embodiment, if Figure 14 As shown, the tension pulley 490 is arranged so as to act on the second belt 443b.

[0273] The mechanical transmission side clutch mechanism 450D may include, for example, a hydraulic actuator (not shown) for operating the tension pulley 490 and a solenoid valve (not shown) for switching the supply and discharge of hydraulic oil to the hydraulic actuator and having its position controlled by the control device 900 .

[0274] Even in the HMT structure 200D having this configuration, the same effects as those of the first embodiment can be obtained.

Claims

1. An HMT structure, characterized in that: have: The HST continuously changes the speed of the rotational power input from the drive source to the pump shaft in a working manner and outputs it from the motor shaft; a planetary gear mechanism including a first element for inputting rotational power at a reference speed transmitted from the driving source, a second element for inputting rotational power of the motor shaft, and a third element for outputting a combined rotational power of the first and second rotational powers; The HMT output shaft is operatively connected to the third element; a shift lever operable to shift the speed in a first operating direction toward a forward side and a reverse side with respect to a zero speed position, and operatively connected to an output adjustment member of the HST such that the rotational speed of the motor shaft varies according to the operating position in the first operating direction; a mechanical rotation applying mechanism capable of inputting the rotational power from the driving source to the second element without passing through the hydraulic transmission path of the HST, and capable of inputting the rotational power at a rotational speed that makes the combined rotational power of the third element zero speed to the second element; An HST-side clutch mechanism that engages and disengages power transmission from the motor shaft to the second element; and a mechanical transmission side clutch mechanism that engages / disengages power transmission from the drive source to the second element via the mechanical rotation applying mechanism; The HST and the planetary gear mechanism are configured such that when the speed change lever is in the zero speed position, the resultant rotational power of the third element becomes zero speed, and as the speed change lever is operated from the zero speed position toward the forward side and the reverse side, the resultant rotational power of the third element increases in speed toward the forward side and the reverse side, respectively. The shift lever is operable from a zero-speed position to a parking position along a second operating direction different from the first operating direction. In response to the operation of the shift lever to the parking position, the HST-side clutch mechanism is switched from the engaged state to the disengaged state, and the mechanical transmission-side clutch mechanism is switched from the disengaged state to the engaged state.

2. The HMT structure according to claim 1, characterized in that The shift operating lever includes a first operating shaft supported to be rotatable about an axis, a second operating shaft supported in an orthogonal state to the first operating shaft, a lever body that is manually operated, a connecting member that connects the base end of the lever body to the second operating shaft, and a lever guide provided with a guide groove for guiding the lever body. The lever body, the connecting member, the second operating shaft, and the first operating shaft can be integrally rotated around the axis of the first operating shaft to perform an operation along the first operating direction, and the lever body and the connecting member can be rotated around the axis of the second operating shaft to perform an operation along the second operating direction. The guide groove includes a first groove for guiding the lever body along the first operation direction and a second groove for allowing the lever body to move in a second operation direction only when the lever body is located at a zero speed position with respect to the first operation direction.

3. The HMT structure according to claim 2, characterized in that The shift operating lever includes an urging member that urges the lever body and the connecting member toward a parking position around the axis of the second operating shaft.

4. An HMT structure, characterized in that: have: The HST continuously changes the speed of the rotational power input from the drive source to the pump shaft in a working manner and outputs it from the motor shaft; a planetary gear mechanism including a first element for inputting rotational power at a reference speed transmitted from the driving source, a second element for inputting rotational power of the motor shaft, and a third element for outputting a combined rotational power of the first and second rotational powers; The HMT output shaft is operatively connected to the third element; a shift lever operable to shift the speed in a first operating direction toward a forward side and a reverse side with respect to a zero speed position, and operatively connected to an output adjustment member of the HST such that the rotational speed of the motor shaft varies according to the operating position in the first operating direction; a mechanical rotation applying mechanism capable of inputting the rotational power from the driving source to the second element without passing through the hydraulic transmission path of the HST, and capable of inputting the rotational power at a rotational speed that makes the combined rotational power of the third element zero speed to the second element; An HST-side clutch mechanism that engages and disengages power transmission from the motor shaft to the second element; and a mechanical transmission side clutch mechanism that engages / disengages power transmission from the drive source to the second element via the mechanical rotation applying mechanism; The HST and the planetary gear mechanism are configured such that when the speed change lever is in the zero speed position, the resultant rotational power of the third element becomes zero speed, and as the speed change lever is operated from the zero speed position toward the forward side and the reverse side, the resultant rotational power of the third element increases in speed toward the forward side and the reverse side, respectively. The shift lever is operable from the zero-speed position to the freewheel position along a second operating direction different from the first operating direction, and is operable from the freewheel position to the parking position along a third operating direction different from the second operating direction. The HST clutch mechanism switches from the engaged state to the disengaged state when the shift lever is operated to the freewheel position, and the mechanical transmission clutch mechanism switches from the disengaged state to the engaged state when the shift lever is operated to the parking position while the HST clutch mechanism remains in the disengaged state.

5. The HMT structure according to claim 4, characterized in that The shift operating lever includes a first operating shaft supported to be rotatable about an axis, a second operating shaft supported in an orthogonal state to the first operating shaft, a lever body that is manually operated, a connecting member that connects the base end of the lever body to the second operating shaft, and a lever guide provided with a guide groove for guiding the lever body. The lever body, the connecting member, the second operating shaft, and the first operating shaft can be integrally rotated around the axis of the first operating shaft to perform operations along the first and third operating directions, and the lever body and the connecting member can be rotated around the axis of the second operating shaft to perform operations along the second operating direction. The guide groove has a first groove that guides the rod body along the first operating direction, a second groove that allows the rod body to move to the freewheel position along the second operating direction only when the rod body is in the zero-speed position with respect to the first operating direction, and a third groove that allows the rod body to move to the parking position along the third operating direction only when the rod body is in the freewheel position with respect to the second operating direction.

6. The HMT structure according to claim 5, characterized in that The shift operating lever includes an urging member that urges the lever body and the connecting member toward a side opposite to a freewheel position around the axis of the second operating shaft.

7. An HMT structure, characterized in that: have: The HST continuously changes the speed of the rotational power input from the drive source to the pump shaft in a working manner and outputs it from the motor shaft; a planetary gear mechanism including a first element for inputting rotational power at a reference speed transmitted from the driving source, a second element for inputting rotational power of the motor shaft, and a third element for outputting a combined rotational power of the first and second rotational powers; The HMT output shaft is operatively connected to the third element; a shift lever operable to shift the speed in a first operating direction toward a forward side and a reverse side with respect to a zero speed position, and operatively connected to an output adjustment member of the HST such that the rotational speed of the motor shaft varies according to the operating position in the first operating direction; a mechanical rotation applying mechanism capable of inputting the rotational power from the driving source to the second element without passing through the hydraulic transmission path of the HST, and capable of inputting the rotational power at a rotational speed that makes the combined rotational power of the third element zero speed to the second element; An HST-side clutch mechanism that engages and disengages power transmission from the motor shaft to the second element; and a mechanical transmission side clutch mechanism that engages / disengages power transmission from the drive source to the second element via the mechanical rotation applying mechanism; The HST and the planetary gear mechanism are configured such that when the speed change lever is in the zero speed position, the resultant rotational power of the third element becomes zero speed, and as the speed change lever is operated from the zero speed position toward the forward side and the reverse side, the resultant rotational power of the third element increases in speed toward the forward side and the reverse side, respectively. When the speed change operating lever is located at the zero speed position, the HST side clutch mechanism is switched from the engaged state to the disengaged state, and the mechanical transmission side clutch mechanism is switched from the disengaged state to the engaged state.

8. The HMT structure according to any one of claims 1 to 7, wherein: The HST-side clutch mechanism includes a bypass valve capable of switching between interruption and communication between a pair of hydraulic oil passages in the HST.

9. The HMT structure according to any one of claims 1 to 7, wherein: An HMT housing for accommodating the HST and the planetary gear mechanism is provided. The HST comprises: the pump shaft having a first end portion located on one side in the axial direction and inputting rotational power from a driving source in an operative manner and a second end portion on the other side in the axial direction; a hydraulic pump supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the pump shaft; the motor shaft arranged parallel to the pump shaft, having a first end portion on one side in the axial direction and a second end portion on the other side, outputting rotational power toward the second element via the first end portion; a hydraulic motor supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the motor shaft, and fluidically connected to the hydraulic pump via a pair of working oil passages; and the output adjusting member capable of changing the volume of at least one of the hydraulic pump and the hydraulic motor. The HMT housing includes an HST space for accommodating the hydraulic pump and the hydraulic motor and a planetary space for accommodating the planetary gear mechanism. The planetary gear mechanism includes: a sun gear that is non-rotatable relative to the first end portion of the motor shaft and functions as the second element; planetary gears that mesh with the sun gear; and an internal gear that meshes with the planetary gears and functions as the first element. and a gear carrier that supports the planetary gears so as to be rotatable about the axis and rotates about the axis of the sun gear in conjunction with the revolution of the planetary gears about the sun gear, functioning as the third element. The internal gear receives rotational power from the drive source via the pump shaft or the HMT input shaft operatively connected to the pump shaft in the planetary space. The mechanical rotation applying mechanism includes a drive gear supported on the second end portion of the pump shaft and a driven gear supported on the second end portion of the motor shaft in a state of direct or indirect meshing with the drive gear, wherein one of the drive gear and the driven gear is rotatable relative to the corresponding shaft and the other is non-rotatable relative to the corresponding shaft. The mechanical transmission side clutch mechanism can switch between engaging and disengaging one of the drive gear and the driven gear with respect to the corresponding shaft. The mechanical rotation applying mechanism and the mechanical transmission side clutch mechanism are housed in a mechanical transmission housing connected to the HMT housing.

10. The HMT structure according to any one of claims 1 to 7, wherein: An HMT housing for accommodating the HST and the planetary gear mechanism is provided. The HST comprises: the pump shaft having a first end portion located on one side in the axial direction and inputting rotational power from a driving source in an operative manner and a second end portion on the other side in the axial direction; a hydraulic pump supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the pump shaft; the motor shaft arranged parallel to the pump shaft, having a first end portion on one side in the axial direction and a second end portion on the other side, outputting rotational power toward the second element via the first end portion; a hydraulic motor supported in a relatively non-rotatable manner at an intermediate portion between the first and second ends of the motor shaft, and fluidically connected to the hydraulic pump via a pair of working oil passages; and the output adjusting member capable of changing the volume of at least one of the hydraulic pump and the hydraulic motor. The HMT housing includes an HST space for accommodating the hydraulic pump and the hydraulic motor and a planetary space for accommodating the planetary gear mechanism. The planetary gear mechanism includes: a sun gear that is non-rotatable relative to the first end portion of the motor shaft and functions as the second element; planetary gears that mesh with the sun gear; and an internal gear that meshes with the planetary gears and functions as the first element. and a gear carrier that supports the planetary gears so as to be rotatable about the axis and rotates about the axis of the sun gear in conjunction with the revolution of the planetary gears about the sun gear, functioning as the third element. The internal gear receives rotational power from the drive source via the pump shaft or the HMT input shaft operatively connected to the pump shaft in the planetary space. The mechanical rotation applying mechanism comprises: a first drive gear supported on the first end portion of the pump shaft in a relatively non-rotatable manner; a first driven gear supported on an idler shaft provided in the planetary space and directly or indirectly meshing with the first drive gear; a second drive gear supported on the idler shaft; and a second driven gear directly or indirectly supported on the first end portion of the motor shaft in a state of directly or indirectly meshing with the second drive gear, wherein one of the first driven gear, the second drive gear, and the second driven gear is rotatable relative to the corresponding shaft and the remaining two gears are non-rotatable relative to the corresponding shaft. The mechanical transmission side clutch mechanism is capable of switching the one gear on and off relative to the corresponding shaft.

11. The HMT structure according to any one of claims 1 to 7, wherein: The mechanical rotation applying mechanism is provided as a belt transmission mechanism operatively connecting the driving source and the motor shaft. The mechanical transmission side clutch mechanism includes a tension pulley capable of switching between engagement and disengagement of power transmission of the belt transmission mechanism.

12. The HMT structure according to any one of claims 1 to 7, wherein: The HST is configured such that, when the shift operating lever is in the zero speed position, the rotational power of the motor shaft becomes a predetermined reverse rotation speed between the neutral speed and the maximum reverse speed; as the shift operating lever is operated from the zero speed position to the maximum forward speed position, the rotational power of the motor shaft changes from the predetermined reverse rotation speed to the maximum forward speed via the neutral speed; and as the shift operating lever is operated from the zero speed position to the maximum reverse speed position, the rotational power of the motor shaft changes from the predetermined reverse rotation speed to the maximum reverse speed. The planetary gear mechanism is configured such that when rotational power at a predetermined reverse rotational speed is input to the second element, the resultant rotational power of the third element becomes zero speed.

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